The present invention is directd to a multi-cavity microwave filter which is optimized to reduce its overall dimensions, electric losses, weight, and manufacturing cost and which further has a simple but mechanically sturdy construction and which may be accurately reproduced.
As is well known, transmission apparatus require microwave filters suitable, in a Tx transmission mode, for eliminating all unwanted and secondary frequencies and for delivering a net signal for transmission. Similarly, at the receiving end, particularly in a Rx reception mode, the filter must filter out unwanted signals and provide an output comprised of useful signals only.
Filters which are used in both the Tx and Rx modes are generally identical to one another and have the same fundamental requirement that they must have very low attenuation characteristics within their passbands and a gradually increasing attenuation characteristic at frequencies which are outside the passband.
Conventionally, multi-cavity microwave filters are produced by employing - (1) a flanged waveguide pipe design - (2) cut or subpieces which are welded together and thereafter machined - (3) microwave filters which are produced from a full ingot. The conventional filters realized in the foregoing manner suffer from many drawbacks, which include: their inherent large sizes and attendant increased costs; complicated manufacturing; poor reproducibility; resistance to automatic machining in numerical control machines; etc.